The present invention relates to a method of drivingly engaging a first motor of a dual motor drive unit with an output shaft of the dual motor drive unit. The present invention further relates to a dual motor drive unit for carrying out the method and to a vehicle comprising a corresponding dual motor drive unit.
Dual motor drive units comprising a first motor and a second motor for driving an output shaft are generally known for their good performance and their high efficiency. Usually, one of the two motors, for example the first motor, is engaged with the output shaft at low output speed and high output torque while it is disengaged from the output shaft at high output speed and low output torque. Thus, dual motor transmissions typically include a mechanism for selectively engaging the first motor with the output shaft, for example a hydraulic clutch. It is generally desirable that the process of engaging the first motor with the output shaft be carried out with maximum smoothness. That is, abrupt variations in gear ratio or traction are to be avoided in order to minimize wear of the mechanical parts and to make the drive unit easier to control.
In order to enhance the smoothness of the engagement process, it has been proposed to equip the clutch with devices such as proportional valves which allow the clutch to be controlled with improved precision. However, the use of these devices usually increases production costs.
Thus, the technical problem underlying the present invention consists of providing an alternative method of engaging a first motor of a dual motor drive unit with an output shaft of the dual motor drive unit. The method should provide a low degree of wear of the mechanical components and a high degree of controllability for the operator. The technical problem underlying the present invention further consists of providing a preferably low cost dual motor drive unit for carrying out the method.